1. Field of the Invention
This invention relates to the field of power supplies, and particularly to power supplies that operate at both high line and low line input voltages.
2. Description of the Related Art
While many electrical devices operate using an input AC line voltage that is an alternating current (AC) input voltage of 120 Volts, it is often desirable to have the same devices operate over a wider range of input voltages. For example, high AC line voltages of around 220 Volts are also in common use. Currently, designers may simply build the power supply to withstand the rigors of the high AC line voltage, since it will also be able to handle the low AC line voltage. This power supply can then operate at both the high AC line voltage and the low AC line voltage.
Unfortunately, while the power supply designed to operate at high AC line voltage will also function with a low AC line voltage input, it will do so inefficiently. In many instances, the efficiency cost of using the same power supply with a low AC line voltage input can be as high as 5%. Where the electrical device is a high-usage device (for example, a server or a rack of servers) that is on for long, continuous periods, this 5% can quickly add up and impose significant costs on the operator.
Currently, designers solve the problem by designing two parallel power supplies—one optimized for high AC line voltage, and the other for low AC line voltage. Based on the input, the appropriate power supply system is used. While this solution allows for high efficiency at either voltage, it also imposes considerable additional cost since the user essentially needs to purchase two power supplies instead of one.